I just did the math in two ways: if each person infects 5 people who have never been infected, it only takes a bit more than 14 cycles from “patient zero” (whoever that was) to infect the entire living human population.

Obviously the real progress of an epidemic isn’t that simple.

Being a retired math teacher I figured this was a perfect case for using logarithms, so I did. (For me, that’s fun!) I went like this:

I’m trying to find n such that five to the nth power equals 7.5 billion, or in math-lingo,

5^n = 7.5*10^9

One takes the logarithms of both sides, and because of the wonderful properties of logs, I get n*log(5)=9+log(7.5) which we can solve for n by dividing both sides by log(5), obtaining

n = (9+log(7.5))/log(5), after which my calculator said n was about 14.1.

But if you have a cell phone you can confirm my result much more easily by asking it work out 5^14. I think you’ll find it’s about six billion; if you try 5^15 you’ll get an enormous umber, over 30 billion, which is much too high. We have only roughly seven and a half billion humans…

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Jerry Hudson

said:Guy –

Hopefully you weren’t felled by the Kung Flu, as I don’t see any postings since March.

I notice that you seem to be associated with Hopewell Observatory. You must have known my friend, Bob Bolster. I last visited Bob several years ago – his health was poor, and he was planning to move to an assisted-living place, I think for Navy guys. I since read that Bob passed away. A most fantastic guy, and I really miss him. He and I both constructed Wright telescopes – his was the 12 inch that you have at Hopewell, and mine was a 10 inch which I have in a small observatory in my back yard here in Concord, CA.

I’ve been looking thru your web page – am thinking of starting one of my own. (Right now, I manage a web site used by our local VFW Post – see below.) Naturally, it will be concerned with telescope projects. If you have any advice, I’d be interested.

Best wishes for the successful outcome of your thin mirror.

– Jerry Hudson (hudsonjk@astound.net).

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